Enantio- and Diastereoselective Spiroketalization Catalyzed by Chiral Iridium Complex.

Iridium-(P,olefin) complex-catalyzed enantio- and diastereoselective formation of substituted spiroketals from racemic, allylic carbonates is reported, which enables the installation of multiple stereogenic centers in a single operation. The protocol was effective for the preparation of a collection of spiroketals of various ring sizes and substituents, including heteroatoms with high enantio- and diastereoselectivity. Furthermore, cascade reactions that couple this enantio- and diastereoselective transformation to additional reversible processes have been achieved to exert concomitant stereocontrol over additional stereogenic centers.